Abstract: In view of the problem that the roof of roadway leaked air to overlying goaf in 49405 working face of Ximing Coal Mine, which lead to the great risk of spontaneous combustion of its residual coal, with the use of FLUENT numerical simulation software, the distribution status and prevention measures of dangerous area of spontaneous combustion in overlying goaf of extremely close lower coal seam were studied. The results show that there is an approximate U-shaped distribution of spontaneous combustion hazard in the overlying goaf due to air leakage in the roadway roof, and under the double action of roadway roof fissures and wind pressure, there are hidden dangers of spontaneous combustion in overlying goaf; the influence of different nitrogen injection on oxygen, temperature and spontaneous combustion dangerous area in overlying goaf is analyzed by single borehole nitrogen injection. It is determined that the optimal nitrogen injection amount of single borehole is 120 m³/h, and the reasonable spacing of nitrogen injection borehole is 36 m.